Leaking alkaline from decades-old US sea barrels created ghostly halos

New research from UC San Diego’s Scripps Institution of Oceanography has revealed that ghostly white halos observed around decades-old corroded metal barrels on the seafloor off Los Angeles are caused by leaking caustic alkaline waste. Initially thought to be linked to toxic pesticide DDT, the halos result from extreme alkalinity (pH ~12) created when alkaline waste reacts with seawater minerals, forming hardened crusts of brucite that cement the sediment and maintain high pH levels. These conditions create seafloor environments similar to natural hydrothermal vents, supporting specialized bacteria adapted to such extremes. The study highlights that this alkaline waste, likely originating from DDT manufacturing and regional industries like oil refining, has persisted for over 50 years, making it a long-lasting pollutant with significant environmental impacts. The white halos provide a visual marker to rapidly assess contamination extent, with about a third of barrels surveyed showing halos. The research emphasizes caution against physically disturbing contaminated sediments, as this could